Thermo Scientific ISQ, User Manual

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7
Optimizing Your Method
Modifying an Automatic Tune
Thermo Scientific ISQ User Guide 93
– Custom —Select this option if you do not want to use the default value for the
tune. For the electron lens negative voltage, the default is -75 V. You should tune
with the same value you are planning to use for your analysis. This value affects
how well the electrons are kept from entering the ion source when they are not
supposed to. If you change your electron energy from 70 V, this value will also
change. This voltage should always be at least 5V below the voltage applied to the
filament. The voltage applied to the filament is the same number, but the
opposite sign, of the electron energy. If you set this value to be smaller than the
electron energy, for example, if the EE is 70 eV, and the negative voltage is set to
-50 V, then electrons can not be stopped from entering the ionization region. If
the negative voltage is set to -75 V, though, the electrons will be blocked from
entering the source. This field is not used at this time.
• Set Ion Source Temperature —Select this checkbox to enable the temperature field.
Then enter a value between 0 and 350 °C (default is 200 °C). The optimal
temperature is determined by the molecular structure and weight of the compounds
you are analyzing. Heavier compounds require a higher temperature. You should set
the temperature as high as possible to keep the ion source clean and maintain the
right amount of sensitivity.
5. Configure the options under the Lenses tab. The lens tune is the main portion of the
tune algorithm. In this section you can choose which components to tune, which mass to
optimize for the tune, what the range of allowed values are, how to move through the
range, how much the signal must change for a new value to be selected, and what (if
anything) should be done about the resolution of the peak and any errors that occur.
Tip If you will be tuning regularly between running sample sets, you can save time waiting
for the temperatures to equilibrate by setting the tune temperatures to the same
temperature used in your acquisition method.
Note Click the Advanced Settings check box to access the Lenses tab.